Motor vehicle manufacturers are constantly striving to provide vehicles which, in the event of a collision, reduce the risk of injury to persons involved in the collision. These persons may be occupants of the vehicle or a pedestrian which is struck by the vehicle. To this end, vehicles are nowadays designed with so-called deformation zones which deform in a controlled manner to thereby absorb energy which arises during impact between the vehicle and an object. The amount of energy which arises in a collision is proportional to the square of the relative velocity between the vehicle and the object at impact. Accordingly, the risk of injury to occupants of vehicles is increased at higher speeds. Due to the considerable amounts of energy which arise as a result of high speed collisions, the deformation zones must exhibit a certain degree of stiffness, or resistance to deformation, to function effectively at those high speeds.
Most collisions between vehicles and pedestrians occur in built-up or urban areas in which the speed of the vehicles is relatively low. For example, most jurisdictions impose a speed limit in urban areas of about 50 km/h. In most collisions, the speed of the vehicle is lower than 40 km/h. Due to the relatively light weight of most pedestrians, the amount of energy arising from a low speed collision between a vehicle and a pedestrian is relatively low. In such situations, the deformation zones of the vehicle may not deform to any great extent and, therefore, a large amount of the energy is transmitted to the pedestrian, possibly resulting in injury.
In addition, a vehicle has certain critical positions that are involved during a collision between a pedestrian and a vehicle. During such a collision between a vehicle and a pedestrian, the pedestrian typically initially impacts the front of the vehicle and, thereafter, the bonnet of the vehicle. Although the bonnet itself may be designed to be relatively deformable, the engine covered by the bonnet is normally not deformable. As a result, the deformation capability of the bonnet is dependent on the size of the clearance between the bonnet and the engine. Several attempts have been made to reduce the head injuries of a pedestrian by certain configurations of the vehicle bonnet, including different configuration that cause the trailing edge of the bonnet to lift. For example, U. S. Pat. No. 5,385,212, granted on Jan. 31, 1995, to John Cady, et al., discloses a vehicle bonnet for motor cars where the vehicle bonnet is lifted to provide a clearance, so that the bonnet may deform to cushion the impact. Such a clearance can be obtained by arranging the bonnet assembly to move rearwardly and pivot when an impact is applied to the leading edge of the bonnet. Such a bonnet is, however, not able to effectively protect a pedestrian in all kind of impact situations. In particular, in a collision between a child and a vehicle the head of the child hits the bonnet at a position much closer to the leading edge of the bonnet.